4-Methylimidazole in soluble coffee and coffee substitutes

Electrochemical detection of 4(5)-methylimidazole in aqueous solutions

4(5)-methylimidazole (4-MeI) is a potential carcinogen widely used in food colours. EU regulations specify a maximum allowable concentration of 200 ppm for 4-MeI in caramel colours. This study reports an electrochemical determination technique for 4-MeI in caramel colours for the first time. The effect of pH and interference from air were studied to optimize the detection conditions on a glassy carbon electrode in aqueous alkaline solutions using square wave voltammetry (SWV) technique. The concentration of 4-MeI was quantitatively measured down to 10 μM (∼0.8 ppm). Traditional methods such as HPLC, GC, spectrometry and immunoassays involve either expensive instrumentation and reagents or time consuming preparation and detection processes. This study demonstrates the possibility of rapid and simple electrochemical determination of (4-MeI) in food colours with minimum workup using a portable potentiostat.

Multivariate optimization for extraction of 2-methylimidazole and 4-methylimidazole from açaí-based food products using polymeric ionic liquid-based sorbent coatings in solid-phase microextraction coupled to gas chromatography-mass spectrometry

In this study, polymeric ionic liquids featuring different functional moieties were applied as sorbent coatings in direct-immersion solid-phase microextraction (DI-SPME) for the extraction of 2-methylimidazole (2-MI) and 4-methylimidazole (4-MI) from açaí-based food products followed by gas chromatography-mass spectrometry (GC-MS) analysis. The analytical method was optimized using a sequential experimental design. Variables used in GC-MS such as desorption time, as well as for SPME-DI, including extraction time, extraction temperature, incubation time of extraction, amount of NaCl in the extract, and stirring rate, were optimized. The fitness-for-purpose of the method was verified by the linearity of matrix-matched calibration curves (R2 ≥ 0.9921), adequate recoveries (81.7-89.7 %), and precision (relative standard deviations ≤11.2 %). The method was applied to twenty-five samples of açaí-based food products. 4-MI was found in four samples whereas 2-MI was not detected above the limit of detection. The method was found to be suitable for quality control analysis.

Probabilistic Risk Assessment of Metals, Acrylamide and Ochratoxin A in Instant Coffee from Brazil, Colombia, Mexico and Peru

This study analysed the probabilistic risk to consumers associated with the presence of iAs, Cd, Cr, Hg, Pb, acrylamide (AA) and ochratoxin A (OTA) in instant coffee from Brazil, Colombia, Mexico and Peru. The results found iAs to be the metal with the highest concentrations (3.50 × 10-2 to 6.00 × 10-2 mg/kg), closely followed by Pb (1.70 × 10-2 to 2.70 × 10-2 mg/kg) and Cr (5.00 × 10-3 to 1.00 × 10-2 mg/kg), although these differences were not significant between countries. Cd and Hg were not detected. Focusing on AA, the concentrations ranged from 1.77 × 10-1 mg/kg (Peru) to 4.77 × 10-1 mg/kg (Brazil), while OTA ranged from 1.32 × 10-3 (Peru) to 1.77 × 10-3 mg/kg (Brazil) with significant differences between countries in both cases. As regards risk, the hazard quotient and hazard index were less than 1, meaning that the consumption of instant coffee represents a low level of concern for non-genotoxic effects. The results of the combination of margin of exposure and probability of exceedance indicated that the non-genotoxic effects of Pb, AA and OTA pose no threat. However, the probability values of suffering cancer from iAs and AA (between 1 × 10-6 and 1 × 10-4) indicated a moderate risk and that management measures should be taken.

The Application of Cold-Induced Liquid-Liquid Extraction for the Determination of 4-Methylimidazole in Tea and Associated Risk Assessment for Chinese Tea Consumers

4-Methylimidazole (4-MEI), as a Maillard reaction product, often occurs in heat-processed food. Due to its widespread occurrence and strong carcinogenicity in food and beverages, 4-MEI has received attention from regulatory organizations and consumers. Some studies have reported the occurrence and exposure of 4-MEI in food, but few studies have involved traditional tea beverages, which is related to the limited analytical methods currently being influenced by complex tea matrices. For this issue, this study presents a simple, reliable, and highly sensitive analytical method for the determination of 4-MEI in tea using liquid chromatography-high resolution mass spectrometry. By means of this method, a total of 570 tea samples from typical tea-producing regions in China were monitored for contamination of 4-MEI. The results showed that the average 4-MEI level (136 μg/kg) in oolong tea was significantly higher than that in other types of tea samples. Based on contamination levels and tea consumption data in China, the daily intake doses (0.04-1.16 μg/day) of 4-MEI among tea consumers were obtained. As a result, the health risk of Chinese tea consumers consuming 4-MEI alone through tea consumption is relatively low, but the overall intake level of 4-MEI in other foods cannot be ignored.

Differential gene expression profiling implicates altered network development in rat postnatal day 4 cortex following 4-Methylimidazole (4-MeI) induced maternal seizures

Compromised maternal health leading to maternal seizures can have adverse effects on the healthy development of offspring. This may be the result of inflammation, hypoxia-ischemia, and altered GABA signaling. The current study examined cortical tissue from F2b (2nd litter of the 2nd generation) postnatal day 4 (PND4) offspring of female Harlan SD rats chronically exposed to the seizuregenic compound, 4-Methylimidazole (0, 750, or 2500 ppm 4-MeI). Maternal seizures were evident only at 2500 ppm 4-MeI. GABA related gene expression as examined by qRT-PCR and whole genome microarray showed no indication of disrupted GABA or glutamatergic signaling. Canonical pathway hierarchical clustering and multi-omics combinatory genomic (CNet) plots of differentially expressed genes (DEG) showed alterations in genes associated with regulatory processes of cell development including neuronal differentiation and synaptogenesis. Functional enrichment analysis showed a similarity of cellular processes across the two exposure groups however, the genes comprising each cluster were primarily unique rather than shared and often showed different directionality. A dose-related induction of cytokine signaling was indicated however, pathways associated with individual cytokine signaling were not elevated, suggesting an alternative involvement of cytokine signaling. Pathways related to growth process and cell signaling showed a negative activation supporting an interpretation of disruption or delay in developmental processes at the 2500 ppm 4-MeI exposure level with maternal seizures. Thus, while GABA signaling was not altered as has been observed with maternal seizures, the pattern of DEG suggested a potential for alteration in neuronal network formation.

4-Methylimidazole, a carcinogenic component in food, amount, methods used for measurement; a systematic review

4-methylimidazole (4-MEI) is widely used industrially. This carcinogenic component has been reported in some types of food. It is usually produced by the caramelization process in food, drinks and caramel coloring. The possible mechanism for the formation of this compound in food is the Maillard reaction. In order to estimate the amount of substance 4-MEI in food, a systematic study was conducted. The selected keywords were 4-methylimidazole, 4-MEI, beverage, drink, meat, milk, and coffee. 144 articles were obtained from the initial search. The articles were evaluated and finally, the data of 15 manuscripts were extracted. Based on the data extracted from selected articles, the highest amount is reported in caramel color, coffee, and cola drinks. In 70% of the selected studies, the analytical method was based on liquid chromatography. In this method, there is no need for derivatization. SPE columns were used to extract samples in most manuscripts. According to per capita consumption, the most exposure to 4-MEI is through coffee. In high risk food products, regular monitoring with analytical methods with high sensitivity is recommended. Furthermore, most of the selected studies were about the validation method, so few samples were selected. It is recommended to design more studies with a high sample size to accurately evaluate this carcinogenic compound in food.

Thermal Contaminants in Coffee Induced by Roasting: A Review

Roasting is responsible for imparting the main characteristics to coffee, but the high temperatures used in the process can lead to the formation of several potentially toxic substances. Among them, polycyclic aromatic hydrocarbons, acrylamide, furan and its derivative compounds, α-dicarbonyls and advanced glycation end products, 4-methylimidazole, and chloropropanols stand out. The objective of this review is to present a current and comprehensive overview of the chemical contaminants formed during coffee roasting, including a discussion of mitigation strategies reported in the literature to decrease the concentration of these toxicants. Although the formation of the contaminants occurs during the roasting step, knowledge of the coffee production chain as a whole is important to understand the main variables that will impact their concentrations in the different coffee products. The precursors and routes of formation are generally different for each contaminant, and the formed concentrations can be quite high for some substances. In addition, the study highlights several mitigation strategies related to decreasing the concentration of precursors, modifying process conditions and eliminating/degrading the formed contaminant. Many of these strategies show promising results, but there are still challenges to be overcome, since little information is available about advantages and disadvantages in relation to aspects such as costs, potential for application on an industrial scale and impacts on sensory properties.

Application of gas flow headspace liquid phase micro extraction coupled with gas chromatography-mass spectrometry for determination of 4-methylimidazole in food samples employing experimental design optimization

Background

4-Methylimidazole (4-MeI) or 4-methyl-1H-imidazole, a slightly yellowish solid with molecular formula C₄H₆N₂, is a heterocyclic compound which supposedly does not exist as a natural product and is formed when carbohydrates are heating with ammonium compounds. This compound is used in pharmaceuticals, agriculture and photography chemicals, dyes and pigments, and rubber manufacturing. In the present study, a simple and efficient sample preparation method designated gas flow headspace liquid phase microextraction (GF-HS-SDME) was employed for the extraction and preconcentration of 4-methylimidazole (4-MeI) from food and beverage samples, before its determination by gas chromatography-mass spectrometry.

Result

To investigate the optimal conditions for the extraction process in GF-HS-SDME method, factors affecting extraction, including selection of extraction solvent, vial volume, extraction solvent ratio, position of extracting solvent, drop volume, sample volume, stirring speed, temperature, extraction time, sample pH, ionic strength of the sample solution and gas flow rate were optimized by utilizing both one-variable-at-a-time method and Plackett–Burman design. The investigation of protocol was carried out by using a standard solution containing 100.0 μg L⁻¹ of 4-MeI in deionized water.

Conclusion

In this study, a simple and green analytical method based on GF-HS-SDME was proposed for the extraction and preconcentration of 4-MeI from foodstuffs, followed by GC–MS determination. The main advantage of this method is its high preconcentration factor and fastness due to the application of an inert gas stream during microextraction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-022-00823-z.

A Review of the Analytical Methods for the Determination of 4(5)-Methylimidazole in Food Matrices

4(5)-Methylimidazole (4(5)MEI) is a product of the Maillard reaction between sugars and amino acids, which occurs during the thermal processing of foods. This compound is also found in foods with caramel colorants additives. Due to its prevalence in foods and beverages and its potent carcinogenicity, 4(5)MEI has received federal and state regulatory agency attention. The aim of this review is to present the extraction procedures of 4(5)MEI from food matrices and the analytical methods for its determination. Liquid and gas chromatography coupled with mass spectrometry are the techniques most commonly employed to detect 4(5)MEI in food matrices. However, the analysis of 4(5)MEI is challenging due to the high polarity, water solubility, and the absence of chromophores. To overcome this, specialized sample pretreatment and extraction methods have been developed, such as solid-phase extraction and derivatization procedures, increasing the cost and the preparation time of samples. Other analytical methods for the determination of 4(5)MEI, include capillary electrophoresis, paper spray mass spectrometry, micellar electrokinetic chromatography, high-performance cation exchange chromatography, fluorescence-based immunochromatographic assay, and a fluorescent probe.

The effect of amino acids on non-enzymatic browning of glucosamine: Generation of butterscotch aromatic and bioactive health compounds without detectable levels of neo-formed alkylimidazoles

A mixture of glucosamine (GlcN, 15% w/v) and different amino acids in 1:1 M ratio was incubated at 70 °C for 12 h. The resulting GlcN-amino acid caramels were analysed for α-dicarbonyl compounds, polyhydroxyalkyl pyrazines, heterocyclic compound and alkylimidazoles. All the analyses were performed by using HPLC-MS/MS followed by pooling the variables with principal component analysis (PCA). GlcN-Gly caramels generated the greatest amount of butterscotch aromatic compound diacetyl and polyhydroxyalkyl pyrazines (fructosazine and deoxyfructosazine). The potentially toxic heterocyclic compound, 5-hydroxymethylfurfural (HMF) was generated in greater amounts with the GlcN-Arg caramels. However, the toxic alkylimidazoles (4-MEI and THI) were not present in any of the GlcN-amino acid caramels. The results suggest that caramel with butterscotch aroma and bioactivity can be produced with GlcN-amino acid at 70 °C. The PCA performed discriminated the majority of the GlcN-amino acid combinations; GlcN-Gly and GlcN-Ser were best discriminated.

Determination of 4(5)-methylimidazole in foods and beverages by modified QuEChERS extraction and liquid chromatography-tandem mass spectrometry analysis

The determination of carcinogenic 4(5)-methylimidazole (4-MeI) in complex matrices at trace levels is a challenge because of its higher polarity and weaker column retention capability. Here, we proposed a novel method for the quantification of 4-MeI in various foods and beverages using modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The evaluated QuEChERS extraction with LC-MS/MS method showed excellent linearity (1-200 μg/L, with correlation coefficient (R²) > 0.999), trueness (91-113%), and precision (relative standard deviation (RSD) ≤ 12.3%), but low matrix effect (92-108%) for cola, tea, beer, coffee beverage, bread, biscuit and instant coffee. The expanded measurement uncertainty was less than 34.4% at 95% confidence level. The proposed method can be successfully applied to determine 4-MeI in 28 commercial foods and beverages purchased from local market. Therefore, we believe this method is likely to provide a potential for 4-MeI determination in practical application.

Chronic intake of 4-Methylimidazole induces Hyperinsulinemia and Hypoglycaemia via Pancreatic Beta Cell Hyperplasia and Glucose Dyshomeostasis

Caramel colours are the preferential food colouring agent globally, reaches wide age groups through eatables. Colas, a sweetened carbonated drink are most common caramel coloured beverage and its consumption is linked with diabetes, obesity, pancreatic cancer and other endocrine disorders. A major by-product produced during caramelization is 4-methylimidazole (4-MEI) that is detected in noteworthy concentrations in colas and other beverages. Previous studies revealed the neurotoxic and carcinogenic potential of 4-MEI in animals at higher doses but the effect of 4-MEI at theoretical maximum daily intake dose on glucose homeostasis is unexplored. Here, mice treated with 4-MEI (32 µg/kg bodyweight/day) for seven weeks exhibited severe hypoglycaemia and hyperinsulinemia mediated by hyperplasia of pancreatic beta cells and induces metabolic alterations. On combinatorial treatment, 4-MEI suppressed the glucogenic potential of non-artificial sweeteners and promotes lipogenesis. Furthermore, increased levels of C-peptide, LDL-cholesterol and triglycerides were observed in the humans with regular intake of 4-MEI containing beverages. In summary, 4-MEI induced pancreatic beta cell hyperplasia and leads to disruption of glucose and lipid homeostasis. This study suggests the need for further assessment and reconsideration of the wide usage of 4-MEI containing caramels as food additives.

A U.S. population dietary exposure assessment for 4-methylimidazole (4-MEI) from foods containing caramel colour and from formation of 4-MEI through the thermal treatment of food

4-Methylimidazole (4-MEI) is formed in caramel colours produced using ammonium compounds (Class III and Class IV caramel colours). 4-MEI can also form in food through Maillard reactions between reducing sugars and amino acids during cooking, roasting or dry-heating. The USFDA has analysed over 700 food and beverage samples collected from 2013 to 2015 for the presence of 4-MEI. These samples include foods containing added caramel colour and foods that are not labelled as containing added caramel colour, but which may contain 4-MEI resulting from thermal treatment. The 4-MEI levels in all food samples were quantified using LC-MS/MS. These data were used to develop a comprehensive dietary exposure assessment for 4-MEI for the U.S. population aged 2 years or more and several sub-populations, using two non-consecutive days of food consumption data from the combined 2009-2012 National Health and Nutrition Examination Survey and 10-14-day food consumption survey data for 2009-2012 from the NPD Group, Inc. National Eating Trends-Nutrient Intake Database. Dietary exposure estimates were prepared for each category of foods labelled as containing added caramel colour and of foods not labelled as containing added caramel colour, but which may contain 4-MEI from thermal treatment. Exposure to 4-MEI from consumption of foods containing added caramel colour was higher than that from foods that contain 4-MEI from thermal treatment for all population groups. Cola-type carbonated beverages were the highest contributors for most populations from foods containing added caramel colour. Coffee was the highest contributor for most populations from foods in which 4-MEI could be formed from thermal treatment. An overall combined exposure to 4-MEI was also estimated that included all foods identified as containing added caramel colour and foods in which 4-MEI could be formed by thermal treatment.

Dispersive liquid-liquid microextraction with in situ derivatization coupled with gas chromatography and mass spectrometry for the determination of 4-methylimidazole in red ginseng products containing caramel colors

A rapid analytical method was developed for the determination of 4-methylimidazole from red ginseng products containing caramel colors by using dispersive liquid-liquid microextraction with in situ derivatization followed by gas chromatography with mass spectrometry. Chloroform and acetonitrile were selected as the extraction and dispersive solvents, and based on the extraction efficiency, their optimum volumes were 200 and 100 μL, respectively. The optimum volumes of the derivatizing agent (isobutyl chloroformate) and catalyst (pyridine), pH, and concentration of NaCl in the sample solution were determined to be 25 and 100 μL, pH 7.6, and 0% w/v, respectively. Validation of the optimized method showed good linearity (R²  > 0.999), accuracy (≥89.86%), intra- (≤6.70%) and interday (≤4.17%) repeatability, limit of detection (0.96 μg/L), and limit of quantification (5.79 μg/L). The validated method was applied to quantify 4-methylimidazole in red ginseng juices and concentrates, 4-methylimidazole was only found in red ginseng juices containing caramel colorant (42.91-2863.4 μg/L) and detected in red ginseng concentrates containing >1% caramel colorant.

Reduction of 4(5)-Methylimidazole Using Cookie Model Systems

The objective of this study was to determine the reduction of 4(5)-methylimidazole (4-MI) under various baking conditions. For 4-MI analysis, an analytical method using gas chromatography-mass spectrometry was developed. The developed method was validated with linearity (r² > 0.999), recovery (101% to 103%, 3 levels), and precision (1.5% to 4.3%, 3 levels). Limits of detection and quantification were 18.5 and 56.0 μg/kg, respectively. This method was used to monitor the level of 4-MI in 11 commercial cookies, which ranged from 71.5 to 1254.8 μg/kg. Time and temperature were modified in the cookie model system to reduce 4-MI. The largest reduction in 4-MI (56%) was achieved by baking at 140 °C for 8 min; however the cookies baked at this condition were not well accepted by consumers. With combination of consumer liking test result, baking cookies at 140 °C for 16 min is optimal for 4-MI reduction (28% reduction), while it has minimal impact on consumer acceptance. A strong correlation (r² = 0.9981) was found between caramel colorant and 4-MI in the cookie model system.

PRACTICAL APPLICATION

A consumer awareness toward toxicity of 4-MI has been arising, and method to reduce the levels of 4-MI in food products are being developed in many studies. Yet, these reduction studies in food model systems only focused on use of food additives for 4-MI reduction. Current study investigated the use of process modification on 4-MI reduction in cookie, and suggested that baking cookies longer at lower temperature, in turn, reduces the levels of 4-MI in cookies without compromising consumer acceptance. Finding from current study can practically aid bakery industry to ensure safety of bakery products without affecting consumer likings.